A

SETUP Strengthens all lower-body muscles; focus is on quads, hamstrings and buttocks; spine extensors and abs work as stabilizers. - Stand with feet slightly wider than hip-width apart, toes turned out at 45-degree angles, knees and hips rotated outward, knees aligned with second toes. - Hold a medicine ball in front of you with both hands, elbows bent and close to sides. - Bend knees into a plié, keeping knees aligned over ankles and lowering hips only as far as you can without changing pelvis position.

B

ACTION - Keeping pelvis still, rise up onto balls of your feet without rotating ankles. - Straighten legs, then squeeze buttocks, keeping heels lifted. - Lower heels to floor, then repeat.